Semiconductor substrates are processed for a wide variety of applications, including the fabrication of integrated devices and microdevices. One method of processing substrates includes depositing a material, such as a dielectric material or a conductive metal, on an upper surface of the substrate. Epitaxy is one deposition process that is used to grow a thin, ultra-pure layer, usually of silicon or germanium on a surface of a substrate in a processing chamber. Epitaxy processes are able to produce such quality layers by maintaining highly uniform process conditions, such as temperature, pressures, and flow rates, within the processing chambers. Maintaining highly uniform process condition in areas around the upper surface of the substrate is necessary for producing the high-quality layers.
Susceptors are often used in epitaxy processes to support the substrate as well as heat the substrate to a highly uniform temperature. Susceptors often have platter or dish-shaped upper surfaces that are used to support a substrate from below around the edges of the substrate while leaving a small gap between the remaining lower surface of the substrate and the upper surface of the susceptor. Precise control over a heating source, such as a plurality of heating lamps disposed below the susceptor, allows a susceptor to be heated within very strict tolerances. The heated susceptor can then transfer heat to the substrate, primarily by radiation emitted by the susceptor.
Despite the precise control of heating the susceptor in epitaxy, temperature non-uniformities persist across the upper surface of the substrate often reducing the quality of the layers deposited on the substrate. Undesirable temperature profiles have been observed near the edges of the substrate as well as over areas closer to the center of the substrate. Therefore, a need exists for an improved susceptor for supporting and heating substrates in semiconductor processing.